Trimming mechanism for sewing machines



July 21, 1936. KUCERA 2,048,268

TRIMMING MECHANISM FOR SEWING MACHINES Filed March 2'7, 1933 2 Sheets-Sheet 1 July 21, 1936. F. A. KUCERA 2,048,268

TRIMMING MECHANISM FOR SEWING MACHINES Filed March 27, 1933 2 Sheets-Sheet 2 Patented July 21,

UNlTED STATES TRIMMING MECHANISM FOR SEWING MACHINES Frank Kucera, Chicago, Ill., assignor to Union Special Machine Company, Chicago, 11]., a corporation of Illinois Application March 27, 1933,:Serial No. 663,078

'3 Claims. (01. 112128) In the stitching of heavy fabrics, it is often desirable to trim the fabric as it is stitched a given distance from the line of stitching. Trimming devices have been provided wherein a reciprocating trimmer works in synchronism with the needle during stitching and trims or severs the fabric along a line parallel with the feed and at a short distance from the line of stitching. The present invention relates to a trimming mechanism of this type, and more particularly to the means for actuating the trimming blade. 1

An object of the invention is to provide a means for securing the trimming blade to the actuating member therefor so that it will be firmly held in place by interengaging parts of metal receiving the end thrust on the trimming blade incident to thesevering of the fabric.

A further object of the invention is to provide a supporting means for .the trimming blade whereby said trimming blade may be shifted to different set positions as it shortens incident to the grinding of the same for sharpening the blade. In the drawings- Figure 1 is a front view of a portion of a machine I embodying the improvements;

Fig. 2 is an end view of a portion of the same with parts broken away to show some of the hidden mechanism; i

Fig. 3 is a view partly in section and partly in plan showing the presser foot and the end of the work supporting arm; 7

Fig.4 is a view from the insideof the needle headshowing the supporting means for the trimming blade; H

; Fig. 5 is a sectional view on the line 55 of Fig. 4; I

Fig. 6 is a perspective view showing the head on the needle bar which supports the trimming blade;

40,. Fig. 7 is a side view of the trimming blade;

Fig. 8 is a view showing diagrammatically fabric sections stitched together and the trimming of the sections along a line parallel with the stitching, and r 45 Fig. 9 is a plan view of the throat plate.

The invention relates to a trimming mecha: nism for sewing machines, and. as illustrated, is applied to a machine which is particularly-adapted for the closing of filled bags. The machine 50; for this purpose is supported so that the work arm is in substantially vertical position and. the fabric sections forming the bag mouth are brought together, and as the filled bag is fed along, the mouth sections of the bag are stitched together 5.5,; and-the portions thereof projecting above the stitching line trimmed a short distance from said stitching line. The machine includes a work arm, a needle head which is arranged so that the needle reciprocates in a horizontal plane, and a looper which cooperates with the needle in the form- 5 ing of enchained stitches. A thread carrying looper is preferably used so that the enchained thread loops will cover and close the needle holes formed in the fabric sections. This is of particular value in connection with the stitching of bags made of 10 paper. A cord is laid along the other face of the bag mouth and the needle passes through this cord, and this cord serves to cover the needle holes on the. side of the bag mouth penetrated by the needle. The present invention has to do with the 15 trimming mechanism used in connection with this stitching mechanism, and while the trimming mechanism is capable of other uses, it is particularly adapted for the trimming of paper fabric sections of a character'used for bags. 20

The trimming mechanism as illustrated includes a trimming blade which is attached to a head carried by a needle bar. The throat plate is provided with an opening into which the trimming blade passes, and one side of the opening 25 serves as a ledger blade to aid in the cutting of the fabric section S. The trimming blade is provided with a series of closely spaced recesses. The supporting head for the trimming blade is provided with a lug or rib adapted to engage one of 30 these recesses. The lug may be shifted from one recess to another for different settings of the blade. A clamping plate overlying the blade firmly holds the blade in place with the lug seated in one of the recesses. This provides interengaging 35 metal parts on the blade and the supporting head therefor which takes the end thrust on the trimming blade incident to the cutting of the fabric sections.

Referring more in detail to the drawings, the sewing machine includes a work arm I within which is disposed a feeding mechanism and the looper mechanism of the stitch forming mechanism. Parallel with the work arm is an arm 2 carrying a needle head 3. A needle bar 4 is mounted for reciprocation in the needle head and carries a needle 5. Cooperating with the needle within this work arm is a thread carrying looper 6. The material is held against the work arm by a presser foot lcarried by a presser bar 8. The material is fed across the work arm by a feeding mechanism which includes a feed dog 9. This feed dog 9 is given its feeding movements by the usual four motion feeding mechanism. Associated with the stitching mechanism is a thread cutter indicated in general at IU which operates to sever the enchained thread loops between stitched articles.

The presser foot is provided with a guard l I at one side thereof and a wire guard l2 at the other side thereof. It is also provided with a guide l3 which directs a cord C through an opening in the presser foot and beneath the presser foot so that the cord will be stitched to the fabric sections and cover the needle holes on the side thereof penetrated by the needle. In Fig. 8 of the drawings, there is shown a portion of a bag, preferably made of paper, in which the side walls B and B are brought together, stitched and trimmed along a line parallel with the line of stitching. The

stitches are indicated at S. The looper 6 cooperates with the needle 5 in the forming of the enchained thread loops, and these enchained loops lie close against the opposite face of the bag mouth covering the needle holes formed therein. This formof bag closure is of the well-known type and forms no part of the present invention, exceptthat the trimming mechanism embodying the invention is particularly adapted for the trimming of paper or other fabrics which may be used inithe making of bags. v V

7 Attached to the lower end of the needle bar 4 is a head H! which supports the needle 5. This head l4 is extended laterally as indicated at l5 and is provided with a recess l6 in the face thereof. The trimming blade is seated in this recess. The trimming blade is indicated at ll in the drawings. This trimming blade is provided with a cutting knife edge is and is preferably curved so that it may be made of considerable length without striking the bearing for theneedle bar. One edge ofthe cutting blade is provided with a series of recesses l9, Is l9 The recess l6 has its side walls 26 and 2| shaped to conform to the curved trimmingblade. Projecting from the side wall 2| is a lug 22 which is curved to conform to the shape of one of the recesses I 9. When the trimming blade is placed in the recess IS, the lug 22 will engage one of the recesses, and this provides interengaging metal parts which will take the end thrust on the trimming blade incident to the cutting of the fabric sections. A cover plate 23 is provided which overlies the trimming blade I1. The extension l5 is provided with arecess 24, and the cover plate 23 extends laterally of the blade into this recess. A clamping plate 25 passes through the cover plate and is threaded into the extension 15. 'The inner face of this cover plate is recessed as indicated at 26 so as to provide aportion 21 that serves as a fulcrum rest for the cover plate, and a portion 28 which contacts with the'blade. This enables the blade to be very firmly clamped in the recess IS. The trimming blade reciprocates in synchronism with the needle, and as the needle penetrates the material during the stitch formation, the trimming blade will move down and contact with the fabric sections and trim the same.

The throat plate is indicated at 29 in the drawings. The throat plate has a needle opening 30 and slots 3| and 32 in which the sections 33 and 34, respectively, of the feed dog 9 operate. There is also a feed section 35 directly in rear of the needle opening which feeds the enchained thread loops between stitched articles and directs the same to the thread cutters. The throat plate is also provided with an opening 36 which conforms to the cross-sectional shape of the trimming blade, andis so dimensioned that the trimming blade can freely move into the opening. The wall 31 of this opening 36 serves, in a measure, as a cooperating ledger blade to support the fabric sections so that the cutting edge will cleanly sever the same. The cutting blade is provided with a point Is and the blade inclines upwardly from this point. As shown in Fig. 2 of the drawings, the point l8 is at the rear and the blade is of such width that this point enters the space formed by the cutting of the fabric sections, and then the blade contacts with the fabric sections a short distance back from the point, and a gradual cutting is accomplished as the blade descends through the fabric sections. The stitch length, of course, may be varied, but the cutting blade is so dimensioned that the point i3 will always pass into the space formed by the cutting blade on its previous reciprocation, so that there is a continuous clean cut of the fabric sections. The cutting blade, it will be noted, is disposed so as to cut the fabric sections from a point in rear of the needle to a point substantially on a line with the needle puncture, so that the cutting of the fabric is in the region where the sections have been joined by the stitching threads. It will also be noted that the feed section 34 is located outside of the opening and feeds the portion of the fabric section which is to be trimmed, positively to a set position for trimming, and also feeds the trimmed off part positively until it is well out from beneath porting head therefor.

As the trimming blade becomes dull, it may be readily removed and ground, and as it shortens, then the lug 22 is placed in another one of the recesses I9, so that the cutting blade will always be positioned for engagement with the fabric section in the normal reciprocation of the needle. This lug and recess provides interengaging metal parts which receive the end thrust on the trimming blade incident to the severing of the fabric sections. The blade has a wide range of movement from a point well above the fabric sections into engagement therewith, and this necessarily causes a heavy endwise thrust on the blade. The ordinary frictional clamping means for the trimming blade is not sufficient, and the blade soon works loose. Applicant, by the positive securing means described above, not only insures that the blade shall remain in the position where it is placed, but also permits it to be shifted to other set positions.

Another advantage derived from placing the cutting edge of the trimmer well up close to the head at the lower end of the needle bar is that the cutter contacts with the fabric just as the needle is reaching the lower end of its stroke. The needle bar is slowing upto reverse its movement when the cutting takes place, and this reduces to some extent, the shock incident to the blade striking the fabric. Furthermore, the needle penetrates the fabric before the cutter contacts therewith, so that the shock incident to the bar to the operating mechanism, a thrust collar is provided on the needle bar directly beneath the usual lug to which the needle lever is connected. This lug is indicated in the drawings at 35 and the thrust collar is indicated at 36. While the trimming device has been described as particularly useful for cutting of heavy fabrics, it is also very efficient in the stitching of paper bags and the trimming of the paper adjacent the line of stitching. It is diflicult to cut the paper bag material during stitching, first because of the thickness and character of the material, and second, because of the long stitch which is used. Usually the machine is adjusted to produce three or four stitches to the inch. The cutter must cut at least a length in the bag material equal to the distance between two needle punctures. Applicant has located his trimming knife on the needle bar and positioned the cutting edge relative to the needle so that the cutter blade effects its cutting action while the needle bar is moving at its slowest speed, that is, just as the needle is reaching the lower end of its stroke. Furthermore, a very firm abutment is made for the trimming blade and notwithstanding the terrific impact of the trimming knife occasioned by the high speed at which the machine operates the paper bag is efiiciently trimmed by the improved trimming mechanism shown.

It is obvious that minor changes in the shaping of the parts and the details of construction may be made without departing from the spirit of the invention as set forth in the appended claims.

7 Having thus described the invention, what I claim as new and desire to secure by Letters Patent, is-

1. In a sewing machine, the combination of a needle bar, a needle supporting head carried thereby, a needle mounted in said supporting head, a trimming blade carried by said supporting head, said trimming blade having closely spaced recesses formed in one edge thereof and said needle supporting head having a lug adapted to engage one of said recesses, said lug and recesses being disposed so as to receive the end thrust on the trimming blade incident to the trimming of the fabric sections.

2. In a sewing machine, the combination of a needle bar, a supporting head carried thereby, a needle mounted in said supporting head, a trimming blade carried by said needle supporting head, said trimming blade having an inclined cutting edge terminating at a point at one side edge of the blade, said side edge of the trimming blade in alinement with the point being provided with a series of closely spaced recesses, said sup- 20 porting head having a lug adapted to engage one of said recesses.

3. In a sewing machine, the combination of a needle bar, a needle carried thereby, a trimming blade carried by the needle b-ar, said needle bar 25 

